Effects of +Gz Loads on Structural Organization of Central Autonomic Nuclei.

Structural alterations in the central autonomic nuclei (dorsal vagal complex and intermediolateral nucleus) of the centrifuged random-bred male rats subjected to +Gz loads were examined. Acute exposure to gravitational loads predominantly produced the reactive changes in these nuclei, while persistently repeated regular loads resulted in cumulation of the destructive alterations. The structural perturbations in the central autonomic nuclei can disturb the autonomic regulation of physiological functions. The character of such disturbances is partially determined by the peculiarities in structural organization of these nuclei.

[MORPHOLOGICAL ASPECTS OF CHANGES IN THE SPINAL GRAY MATTER DUE TO G-LOADS IN EXPERIMENT].

To study changes in spinal cord structures brought about by g-loads, laboratory animals (rats) were rotated on a centrifuge following a special procedure. Systematic g-loads along the craniocaudal axis resulted in reactive alterations, and also obvious destructive processes in the spinal gray matter (SGM). Light optical microscopy discovered that part of neurons had bodies with less intensive dying. Electron microscopy showed that among the cytoplasmic structures mitochondria were particularly sensitive to g-loads, which could affect mitochondrial oxidation. In the lumbar, these changes were observed in every segment under study; they were more significant in comparison with those found in cervical and thoracic segments of the spinal cord. Interneuron disintegration at neural centers revealed itself by the "light" type degeneration of synapses. Changes in capillaries included nuclei deformations and destruction of organelles in endotheliocytes, pericapillary edema, and erythrocytes sludge in the lumen. Inequality of spinal cord changes suggests the mosaic pattern of their distribution. Furthermore, their manifestation grew with the cranicaudal gradient so that the most conspicuous destructive developments occurred in the lumbar but not in the thoracic let alone the cervical segment. Acute g-loads gave rise to reactive changes in neurons and interneuron synapses that were the morphological markers of increased functional activity of neurons and activation of interneuron firing. In addition to the reactive changes, chronic g-loading also produced destructive disorders in GSM structures. These changes were not observed following acute g-loads and, therefore, resulted from multiple g-exposures and were cumulative.

[ROLE OF THE SYMPATHOADRENOMEDULLARY SYSTEM IN FORMATION OF PILOT'S ADAPTATION TO FLIGHT LOADS].

Purpose of the work was to evaluate the sympathoadrenomedullary functions and associated psychophysiological reactions of pilots as a function of flight hours on highly maneuverable aircraft. Volunteers to the investigation were 78 pilots (41 pilots of maneuverable aircraft and 37 pilots of bombers and transporters). Selected methods were to enable comprehensive evaluation of the body functioning against flight loads. Our results evidence that piloting of high maneuverable aircraft but not of bombing and transporting aircrafts activates the sympathoadrenomedullary system significantly. This is particularly common to young pilots with the total flying time less than 1000 hours. Adaptive changes to flight factors were noted to develop with age and experience.

[Structural-functional reserves of the vegetative nervous system in pilots flying high maneuver aircrafts].

Purpose of the work was to analyze morbidity among pilots of different categories of aircraft, and to investigate reactivity of the vegetative nervous system (VNS) in pilots flying high maneuver aircrafts varying in age and flying time. Morbidity was deduced from the data of aviation medical exams. The VNS investigation involved 56 pilots of fighter and assault aircrafts both in the inter-flight periods and during duty shifts. Cytochemistry was used to measure glycogen in peripheral blood neutrophils in 77 pilots. It was shown that the pre-stress condition in pilots with the flying time more than 1000 hours may transform to chronic stress, provided that the flight duties remain heavy. According to the cytochemical data, concentration of neutrophilic glycogen indicating the energy potential of peripheral blood leukocytes is controlled by hormones secreted by the VNS sympathetic and parasympathetic components.

[Sympathetic and parasympathetic centers of the brain and spinal marrow of rats during exposure to +Gz].

Structural transformations in the dorsal vagal complex and intermediolateral nucleus due to +G, loads were studied in white outbred male rats centrifuged according to the standard procedure (P.S.Paschenko, 1995). Methods of investigation included light and electron microscopy, morphometric analysis and statistical analysis. Acute exposure to +Gz loads resulted in essentially reactive changes in the centers under study. At the same time, regular exposure to this extreme factor led to cumulation of destructive changes. The peculiar structure of the centers governs uniqueness of disorders which may unbalance the autonomous regulation of organism functions.

Structural transformations in sympathetic ganglia and the thoracic part of the vagus nerve in conditions of gravitational overloading.

The aim of the present work was to undertake a complex of studies of structural transformations in the anterior thoracic ganglia of the sympathetic trunk and the thoracic part of the vagus nerve after acute and chronic gravitational overloading (GOL). Studies were performed on 28 white mongrel male rats aged 8-21 weeks. Animals of series I (acute GOL) were rotated in a centrifuge on one day (three rotation sessions with two 20-min breaks, giving a total rotation time of 31 min). Animals of series II (chronic GOL) were rotated in an alternating two-week regime for 13 weeks (total rotation time 20 h 9 min). Rotation was performed in the craniocaudal direction with overloads of 4-6 g. Intact rats served as controls. Histological, electron microscopic, and morphometric analyses were performed. Acute GOL produced mainly reversible reactive changes in the anterior thoracic nodes of the sympathetic trunk and thoracic part of the vagus nerve, probably induced by unusual combinations of afferent spike activity of unusual strength, this probably being one of the causes of impairments seen after rotation. Chronic GOL was followed by the development of mainly destructive and compensatory-adaptive processes, characterized by the destruction of mitochondrial cristae, vacuolization of neuron cytoplasm, and degradation of interneuronal synapses. These changes were probably due to the development of hypoxia, which leads to interneuronal synaptic blockade in sympathetic ganglia. These structural transformations demonstrate the involvement of both the sympathetic and parasympathetic compartments in responses to acute and chronic GOL, providing evidence of the generalization of adaptive processes in the autonomic nervous system.

[Changes in the pancreas structure after exposure of the body to gravitational overloads].

The aim of this study was to determine the changes in the pancreas structure after acute and chronic exposure of organism to gravitational overloads (GO). The experiments were conducted in 36 outbred albino male rats, 12 rats formed the control group. GO effect was modeled using the centrifuge; the value of the overload thus created amounted to 4,0-6,0 gravitational units. Pancreas structure was studied using histological, electron microscopic and morphometric methods. It was found that after acute exposure to GO, mainly the reactive changes were demonstrated all the pancreatic structures studied: acinocytes, endocrinocytes, blood vessels and nervous apparatus. Chronic exposure to GO resulted in both reactive modifications, similar to those described after an acute exposure, and various compensatory-adaptive and destructive changes.

[Structural modifications of the thoracic region of vagus and sympathetic trunk ganglia after exposure to gravitational overloads].

The aim of this work was the complex study of structural modifications in the anterior thoracic ganglia of the sympathetic trunk and in thoracic region of vagus after acute and chronic exposure to gravitational overloads (GO). The study was carried out in 28 albino outbred male rats aged 8-21 weeks. Animals of group I (acute exposure) were rotated in the centrifuge during one day (3 rotations with 2 20-min breaks; total exposure duration was equal to 31 min. Animals of group II (chronic exposure) were treated intermittently during 2-weeks-long periods for 13 weeks; total exposure duration was equal to 20 hours 9 min. Gravitation was applied in cranio-caudal direction with the overload of 4-6 gravitational units. Intact rats served as a control. Material was studied using histological, electron microscopic and morphometric methods. The study of the sympathetic trunk and thoracic ganglia following acute GO have revealed mainly the reactive and reversible changes, probably caused by the appearance of an afferent impulsation of unusual intensity and combination, which is one of the reasons of the disturbances, observed after rotation. Following chronic GO, destructive and compensatory-adaptive changes prevailed; these were characterized by the mitochondrial cristae destruction, vacuolization of neuronal cytoplasm, destruction of interneuronal synapses. These changes, were probably, the result of hypoxia leading to the development of interneuronal synaptic block in sympathetic ganglia. The structural modifications described are indicative of the involvement of both sympathetic and parasympathetic parts of the autonomic nervous system in the response to acute and chronic GO, suggesting the generalization of the adaptation processes in the autonomic nervous system after GO.

[Structural changes in spinal cord gray matter induced by gravitational overloads]. / Strukturnye preobrazovaniia v serom veshchestve spinnogo mozga posle vozdeistviia gravitatsionnykh peregruzok.

After acute exposure of rats to gravitational overloads (GO) the reactive changes in neurons and interneuronal synapses of spinal cord were found. These are interpreted as morphologic signs of increased functional activity of neurons and activation of interneuronal impulse transmission. Chronic application of GO results in both reactive changes and damage of spinal cord structures. These changes were not seen after an acute exposure to GO, and thus they are associated with the repeated GO, indicating GO cumulative effect. Administration of "Vitavis" provides a membrane-protective effect, especially in respect to mitochondria of neurons and perineuronal glial cells in cervical and thoracic segments of spinal cord. The effect was less pronounced in spinal cord lumbar segments as a result of pericapillary edema, preventing the transport or drug from capillary bed to the neural structures.

[The structural organization of the normal rat area postrema and under conditions of chronic exposure to gravitational loads]. / Strukturnaia organizatsiia area postrema krysy v norme i v usloviiakh khronicheskogo vozdeistviia gravitatsionnykh peregruzok.

Topography and structure of rat area postrema were specified using light optic and electron microscope. Disturbance of liquor-encephalic transport (hydrops of ependymocytes), sharp changes of cytoplasmic organelles in neurons, signs of intercellular desintergration (synapse degeneration after "clear" type), death of part of neurons, disorder in secretory processes in neuroendocrine cells were shown to occur following chronic effect of gravitation overloads, in its structural elements. These changes take place on the background of hemomicrocirculatory disturbances, appearance of connective tissue fibres in perivascular space of Virchow-Robin and are probably conditioned by a developing circulatory hypoxia.